Apparatus for the automated folding, such as C-folding and Z-folding, of letter-size and similar sheets are well-known. It is also generally known to provide such apparatus in conjunction with a copier or digital printer, for folding print sheets which those machines output.
A typical folding apparatus includes three selectably-contacting rollers, forming two nips between adjacent pairs of rollers. For a sheet being folded, a portion of the length of the sheet is caused to buckle near one of the nips, until that portion of the sheet is contacted by two rollers and drawn through the nip. The drawing of the sheet through the nip results in a sharp fold. For different types of folding of a sheet, such as C-folding and Z-folding, different portions of the sheet are caused to buckle in a predetermined sequence adjacent different nips. In order to cause the buckling of the correct portion of the sheet, the edge sheet is typically pushed against a stop surface in a fixed position relative to the nip.